The production of algae, as a protein rich food source for animals and humans, as well as a source of other valuable products such as dyes, vitamins and the like, is extensively reported in the Carnegie Institution of Washington publication No. 600, ALGAL CULTURE FROM LABORATORY TO PILOT PLANT, Edited by John S. Burlew and published at Washington, D. C. in 1964. This publication contains studies of the various factors involved in obtaining high yields from cultures of algae, focusing primarily on the species Chlorella pyrenoidosa but of applicability to other species of algae as well. In addition, the above publication and other prior art including U.S. Pat. No. 2,732,661 disclose the cultivation of algae under conditions which cause a predominance of intracellular protein, lipid or carbohydrate by regulating the amount of available nitrogen. Production of algae as a source of proteins and lipids, and other materials derived from the algae, are discussed in the Carnegie publication.
According to another body of prior art, utilization of bacterial polysaccharides as flocculating agents, especially for aggregating soil particles, thereby improving soil structure is known. Patents such as U.S. Pat. Nos. 2,780,888 and 2,901,864 teach the application of these bacterially produced biopolymers to the soil as a means for promoting soil aggregation, thereby producing a granular structure which is sufficiently porous to allow air, water, and plant roots to penetrate through the soil. According to these patents, sucrose as a raw material is converted to dextran by innoculating a nutrient medium containing sucrose with a dextran synthesizing bacteria such as Leuconostoc mesenteroides. The dextran may be used in granular form or in solution in an aqueous medium and applied to soil.
In addition to the foregoing, long chain synthetic polymers useful as soil conditioning agents which are capable of aggregating soils and useful for other applications where flocculating activity is required, are disclosed in the art. Examples of synthetic polymeric materials useful for increasing aggregation in surface soil are disclosed in Hedrick et al U.S. Pat. No. 2,651,885. According to the Hedrick et al patent, water soluble polymeric electrolytes having a molecular weight of at least 10,000, including polymers of acrylic acid, co-polymers of maleic anhydride and the like are provided. These polymeric materials are effective in improving soil structure, but their use has been somewhat limited in view of their high cost.